They need further income, but what they cannot do is jeopardise their capital when there is little opportunity of replacing it.

An increasingly popular answer is to start an online business.

Upfront costs can be kept to a minimum and the business can be run cheaply from a living room.

For those retirees who have already downsized and moved out of a city, there is no problem. With an internet connection your business can thrive from anywhere.

"We often assume founders look a certain way - young, white, casually dressed and male - but that myth simply isn’t true. Innovation can and should come from everywhere."

Sarah Drinkwater, head of Campus London

Tricia Cusden, 67, wasn't sure if she had sufficient funds to start a business.

Decades ago Ms Cusden was told by a financial adviser that as a divorced 42-year-old, the best way to provide for herself was to get married again - to a rich man.

“I thought: 'you stupid man, that can’t be the only solution'."

She went on to invest in property, including a ruin in France which she converted into a holiday home.

By the time she retired at 65, she had a spare £40,000 in a savings account available to invest.

This was the most she was prepared to risk setting up Look Fabulous Forever, a makeup range and tutorial website for older women. The ethos was that clients could look good at any age - be it 19 or 90.

After taking risks with property, Ms Cusden had £40,000 she could afford to lose

“I could afford to lose it, so why not use it creatively?” she said.

Securing sufficient finances to fund a start up is a challenge for anyone.

Pension freedoms, introduced in April 2014, allow over-55s access to their pension savings - potentially opening up a new source of finance for older entrepreneurs.

Through a combination of low overheads and successful sales, Look Fabulous Forever made two and a half times its original investment in the first year, and Ms Cusden says it has not been in debt for a day.

“When I started it, I decided I didn’t want to lose sleep over this business. I never allowed a situation where we had outstanding invoices to pay without income to cover it.

"If we had £10,000 worth of invoices in the pipeline to pay, that would mean losing sleep.”

Louise Chunn, 59, founder of online therapist directory, Welldoing.org said that while some people spend lots of money on offices and equipment, she and her two members of staff work from a table in her spare room.

One day a week they work from a cafe within Google's Campus London in the heart of the capital's "Silicon Roundabout", Shoreditch.

Ms Chunn says it is a good way to energise themselves and “to feel like we’re part of the whole start-up culture”.

Ms Chunn says it's hard working freelance after years of earning a regular income as a senior executive

Like Ms Cusden, Ms Chunn started her business in 2013 with about £40,000, half of which was put in by her husband.

Former editor Ms Chunn said she was disillusioned with finding another job in the publishing industry.

She spent about eight months coming up with the idea of Welldoing.org, after experiencing the difficulty of trying to find a therapist in her part of London.

Specialists pay to be listed on the site, although Ms Chunn says there is "a little way to go" before the site breaks even.

With over twenty years experience in women’s magazines and having been the former editor of Instyle and Good Housekeeping, Ms Chunn says she finds the erratic nature of freelance work and being supported by her husband challenging.

"My advantage is I’ve lived. I’m a person with experience and knowledge that things can go wrong in life and in business"

However, she regards her age as a bonus when it comes to dealing with difficult situations.

“My advantage is I’ve lived. I’m a person with experience and knowledge that things can go wrong in life and in business. It wouldn’t be appropriate if someone was doing this at 23.”

Useful Music founder, Graham Lyons, 79, is different from some retiree entrepreneurs in that he founded his first business in 1983. It was a music publishing business from home and funded with just £5,000.

A few years later, aged 50, he invented a "mini-clarinet" designed to allow children to start learning the instrument four years earlier than is usual.

But he was well into his 70s when he moved his publishing business online - something he knew he needed to do if it were to continue to thrive.

Mr Lyons said when it came to raising finance he wrote to 50 people in music education, offering shares of 1pc for £2,000, he managed to convince half of them to invest.

As her business grew, Ms Cusden also sought investment beyond her initial £40,000.

She went to her family as well as four external individuals.

“I considered taking a mortgage on my home, but then decided it was madness.

“I didn’t think I’d have the time to recoup any losses. I could end up in my 70s with a stupid mortgage and be in a horrible situation. If I’d been 45, I’d have taken the risk.

“I would have been stupid to impoverish myself into old age with some reckless decision.”

Sarah Drinkwater, head of startup workspace at Google's Campus London, says age is a bonus.

"For those first-time founders, their age gives them a clear advantage; often, they have decades of experience and contacts to draw on, and can sometimes bootstrap (or self fund) their startups far longer than those in their early twenties.

"The challenges of starting a company at this time in life are what we tried to address with our Founders over 50 program: the lack of a support network and visibility within the startup scene.

"We often assume founders look a certain way - young, white, casually dressed and male but that myth simply isn’t true. Innovation can and should come from everywhere."